Proposed resolution:

This wording is relative to N4659.

1. Edit [fs.filesystem.syn] as indicated:

   path canonical(const path& p, const path& base = current_path());
   path canonical(const path& p, error_code& ec);
   path canonical(const path& p, const path& base, error_code& ec);
   

2. Edit [fs.op.canonical] as indicated:

   path canonical(const path& p, const path& base = current_path());
   path canonical(const path& p, error_code& ec);
   path canonical(const path& p, const path& base, error_code& ec);
   

   -1- Effects: Converts p, which must exist, to an absolute path that has no symbolic link, dot, or dot-dot elements in its pathname in the generic format.

   -2- Returns: A path that refers to the same file system object as absolute(p, base). For the overload without a base argument, base is current_path(). SignaturesThe signature with argument ec returns path() if an error occurs.

   […]

[ 2017-07-14, Toronto, Moved to Immediate ]

[ 2017-07-14, Toronto, Davis Herring provides wording ]

[ 2017-06-27 P1 after 5 positive votes on c++std-lib ]

Davis Herring: This needs to be P1 — due to a wording gap in P0492R2, 2 out of the 3 overloads of filesystem::canonical() have bad signatures and are unimplementable.

This is from editorial issue #1620:

Since the resolution of US-78 was applied (as part of P0492R2), std::filesystem::absolute(path, base) no longer exists. However, std::filesystem::canonical is still defined in terms of absolute(p, base).